Aerospace Engineeringhttp://hdl.handle.net/1903/2206
Tue, 26 Sep 2017 21:40:30 GMT2017-09-26T21:40:30ZRefined Performance and Loads of a Mach-Scale Rotor at High Advance Ratioshttp://hdl.handle.net/1903/20030
Refined Performance and Loads of a Mach-Scale Rotor at High Advance Ratios
Trollinger, Lauren Nicole
This work will investigate the performance and vibratory loads of a Mach-scale rotor with highly similar, non-instrumented blades at advance ratios (µ) up to 0.9. Wind tunnel tests were performed on a 4-bladed, articulated rotor with a diameter of 2.78 ft. The slowed rotor was operated at 30%, 40%, and 50% of nominal speed,corresponding to advancing tip Mach numbers up to 0.53, and shaft tilt angles
of -4◦, 0◦, and 4◦ were tested. Collective sweeps from -2◦ to 12◦ were performed for each flight condition, and blade motion, control cyclics, and hub loads were measured. Blade similarity was shown to improve rotor track and trim at high µ. Thrust reversal was observed at µ = 0.9, but positive (aft) shaft tilt increased lift at high µ. Vibratory hubloads are shown to increase with advance ratio. Correlations performed using the comprehensive analysis code UMARC show good agreement for rotor performance.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1903/200302017-01-01T00:00:00ZHAMSTRAN, AN INDIRECT METHOD TO CREATE ALL- QUADRILATERAL GRIDS FOR THE HAMSTR FLOW SOLVERhttp://hdl.handle.net/1903/20021
HAMSTRAN, AN INDIRECT METHOD TO CREATE ALL- QUADRILATERAL GRIDS FOR THE HAMSTR FLOW SOLVER
Zhu, Zihao
HAMSTR is a newly developed flow solver that utilizes Hamiltonian paths and strand grids for three-dimensional flows on overset and hybrid meshes. In order to use HAMSTR, it is required that one has a decent all-quad surface mesh; this is the motivation for the development of HAMSTRAN. It is an indirect method to create an unstructured all-quadrilateral 3D surface mesh and strand templates for each vertex. It transforms triangular as well as quad-dominant surface meshes into all-quad meshes, without any smoothing steps. The proposed method is fast and can work on highly complicated surfaces with lots of sharp features while producing a minimum number of irregular grids. HAMSTRAN is mostly based on the Q-Tran algorithm, but it has many advantages over Q-Tran. For example, HAMSTRAN is not only able to utilize an all-triangular mesh, but can also use quad-dominant and hybrid meshes as input and generate a decent all-quad mesh. After creating the surface mesh, HAMSTRAN proceeds to create the strand templates for each vertex. The strand templates are vectors extruding from the surface in the wall-normal direction without crossing each other. The direction of the vectors can be adjusted according to the 3D volume mesh required for the future flow solving process. Several examples will be presented to demonstrate the efficiency of this method, such as for airfoils, wings, rotor blades and fuselage.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1903/200212017-01-01T00:00:00ZGRAMIAN-AWARE CLOSED LOOP FLIGHT CONTROL DESIGN FOR ENERGY HARVESTING THROUGH MODULATING DISTURBANCE SENSITIVITYhttp://hdl.handle.net/1903/20019
GRAMIAN-AWARE CLOSED LOOP FLIGHT CONTROL DESIGN FOR ENERGY HARVESTING THROUGH MODULATING DISTURBANCE SENSITIVITY
Saxena, Utsav
Many desired micro aerial vehicle missions are significantly larger than the mission endurance of the vehicles. Due to extreme constraints on size, weight and power available, small scale air vehicles are highly sensitive to atmospheric disturbance. This work introduces a control-theoretic framework that models the magnitude of the vehicle's disturbance sensitivity and observability in conjunction with each other under a gramian-based formulation. To implement atmospheric gust response modulatiom, a ``gramian-aware'' flight control law is designed using open loop plant models across various scales and assuming perfect gust measurement. Time-domain system identification was conducted using data collected from repeatable automated flights in a motion capture arena in order to derive the plant model. Closed-loop simulation results as well as experimental data modulating the plant using cruise speed are presented to illustrate that the gramian-based control laws can be utilized to facilitate atmospheric energy scavenging in gusting environments.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1903/200192017-01-01T00:00:00ZSizing Tool for Quadrotor Biplane Tailsitter UAShttp://hdl.handle.net/1903/19983
Sizing Tool for Quadrotor Biplane Tailsitter UAS
Strom, Eric
The Quadrotor-Biplane-Tailsitter (QBT) configuration is the basis for a mechanically simplistic rotorcraft capable of both long-range, high-speed cruise as well as hovering flight. This work presents the development and validation of a set of preliminary design tools built specifically for this aircraft to enable its further development, including: a QBT weight model, preliminary sizing framework, and vehicle analysis tools. The preliminary sizing tool presented here shows the advantage afforded by QBT designs in missions with aggressive cruise requirements, such as offshore wind turbine inspections, wherein transition from a quadcopter configuration to a QBT allows for a 5:1 trade of battery weight for wing weight. A 3D, unsteady panel method utilizing a nonlinear implementation of the Kutta-Joukowsky condition is also presented as a means of computing aerodynamic interference effects and, through the implementation of rotor, body, and wing geometry generators, is prepared for coupling with a comprehensive rotor analysis package.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1903/199832017-01-01T00:00:00Z